Shaq does shark week. Ronda Rousey against a bull shark. Bear Grylls faces off with … yes … a shark. Shark Week is full of celebrities having close encounters with one of the ocean’s greatest predators, but did you know early astronauts were also prepared for their own tussle with the fearsome fish?

Training underwater for extravehicular activity (EVA)—popularly known as spacewalking—is now critical for preparing astronauts to work in weightlessness. But when cosmonauts and astronauts first ventured outside their spacecraft 50 years ago, in 1965 and 1966, they had no such training. Spacewalking did not appear difficult, nor did space program officials think that underwater work was needed. In the United States, it took Eugene Cernan’s June 1966 Gemini IX EVA to change attitudes. Fighting against his pressurized suit, while trying to do work without adequate handholds and footholds, Cernan quickly became exhausted and overheated. Only afterward did NASA Manned Spacecraft Center in Houston reach out to a tiny company outside Baltimore: Environmental Research Associates, Inc. (ERA). Funded by another agency center, it had been experimenting with EVA simulation in a rented school pool on nights, holidays, and weekends. That project became the foundation for Houston’s first underwater training facility.

Gene Kranz is best known for his stellar performance as flight director for the ill-fated Apollo 13 mission. But Kranz is also known for another thing: his white vests. Kranz’s vests had legendary status around mission control, and also in the minds of the public after actor Ed Harris wore an exact replica of Kranz’s most famous vest in the 1995 movie, Apollo 13. Kranz’s vests represented the strong and can-do approach that pervaded his mission control team, especially during the Apollo 13 mission in which the astronauts’ lives were at stake.